The assumption that Natural Law is binding on states inter seis the next in rank of those which underlie International Law. Aseries of assertions or admissions of this principle may betraced up to the very infancy of modern juridical science, and atfirst sight it seems a direct inference from the teaching of theRomans. The civil condition of society being distinguished fromthe natural by the fact that in the first there is a distinctauthor of law, while in the last there is none, it appears as ifthe moment a number of units were acknowledged to obey no commonsovereign or political superior they were thrown back on theulterior behests of the Law Natural. States are such units; thehypothesis of their independence excludes the notion of a commonlawgiver, and draws with it, therefore, according to a certainrange of ideas, the notion of subjection to the primeval order ofnature. The alternative is to consider independent communities asnot related to each other by any law, but this condition oflawlessness is exactly the vacuum which the Nature of thejurisconsults abhorred. There is certainly apparent reason forthinking that if the mind of a Roman lawyer rested on any spherefrom which civil law was banished, it would instantly fill thevoid with the ordinances of Nature. It is never safe, however, toassume that conclusions, however certain and immediate in our owneyes, were actually drawn at any period of history. No passagehas ever been adduced from the remains of Roman law which, in myjudgment, proves the jurisconsults to have believed natural lawto have obligatory force between independent commonwealths; andwe cannot but see that to citizens of the Roman empire whoregarded their sovereign's dominions as conterminous withcivilisation, the equal subjection of states to the Law ofNature, if contemplated at all, must have seemed at most anextreme result of curious speculation. The truth appears to bethat modern International Law, undoubted as is its descent fromRoman law, is only connected with it by an irregular filiation.
The early modern interpreters of the jurisprudence of Rome,misconceiving the meaning of Jus Gentium, assumed withouthesitation that the Romans had bequeathed to them a system ofrules for the adjustment of international transactions. This "Lawof Nations" was at first an authority which had formidablecompetitors to strive with, and the condition of Europe was longsuch as to preclude its universal reception. Gradually, however,the western world arranged itself in a form more favourable tothe theory of the civilians; circumstances destroyed the creditof rival doctrines; and at last, at a peculiarly felicitousconjuncture, Ayala and Grotius were able to obtain for it theenthusiastic assent of Europe, an assent which has been over andover again renewed in every variety of solemn engagement. Thegreat men to whom its triumph is chiefly owing attempted, it needscarcely be said, to place it on an entirely new basis, and it isunquestionable that in the course of this displacement theyaltered much of its structure, though far less of it than iscommonly supposed. Having adopted from the Antonine jurisconsultsthe position that the Jus Gentium and the Jus Naturae wereidentical, Grotius, with his immediate predecessors and hisimmediate successors, attributed to the Law of Nature anauthority which would never perhaps have been claimed for it, if"Law of Nations" had not in that age been an ambiguousexpression. They laid down unreservedly that Natural Law is thecode of states, and thus put in operation a process which hascontinued almost down to our own day, the process of engraftingon the international system rules which are supposed to have beenevolved from the unassisted contemplation of the conception ofNature. There is too one consequence of immense practicalimportance to mankind which, though not unknown during the earlymodern history of Europe, was never clearly or universallyacknowledged till the doctrines of the Grotian school hadprevailed. If the society of nations is governed by Natural Law,the atoms which compose it must be absolutely equal. Men underthe sceptre of Nature are all equal, and accordinglycommonwealths are equal if the international state be one ofnature. The proposition that independent communities, howeverdifferent in size and power, are all equal in the view of the lawof nations, has largely contributed to the happiness of mankind,though it is constantly threatened by the political tendencies ofeach successive age. It is a doctrine which probably would neverhave obtained a secure footing at all if international Law hadnot been entirely derived from the majestic claims of Nature bythe Publicists who wrote after the revival of letters.
